US Navy photo showing the shattered remnants of the south tower of the World Trade Center in New York City following the devastating terrorist attack on September 11 2001. The remains stand like a tombstone under the blue sky in the image captured by Journalist 1st Class Preston Keres on September 14 2001. The Twin Towers collapsed less than two hours after two out of four hijacked airliners were deliberately crashed into them as part of a co-ordinated Al-Qaeda suicide attack which killed thousands of people. A third airliner was crashed into the Pentagon in Virginia and a fourth crashed into a field in Pennsylvania as passengers fought to retake control.